"Crossover Design for New Project"

[GM]

OK, I came up with ~18.56 ft^3 (~525.56 L) net which is about right for one driver tuned to ~30 Hz, so only ~half size for two, ergo raises F3 ~1.4x into the 40s, but corner loading hopefully will shift it back down a bit and with 107+ dB/sens/stereo +room/corner gain there's plenty for shelving EQ to flatten it out to Fb in-room.

Since the lowest Fs = 25 Hz, for now we'll assume it's the lowest tuning with the highest being ~40 Hz based on averaging everything out, though sealed is theoretically looking best overall if there's some half decent room gain.

You can use a rectangular duct vent, it's just more hassle to adjust its length and why I suggested a removable vent plate.

Anyway, looks like ~25 Hz Fb = 16.875" W x 3" H slot x 4" long vent and baffle thickness cutout = ~30 Hz, so this would be the minimum size cutout spaced up off the cab floor ~3".

GM

[Altec Best]

OK, I came up with ~18.56 ft^3 (~525.56 L) net which is about right for one driver tuned to ~30 Hz, so only ~half size for two, ergo raises F3 ~1.4x into the 40s, but corner loading hopefully will shift it back down a bit and with 107+ dB/sens/stereo +room/corner gain there's plenty for shelving EQ to flatten it out to Fb in-room.

Since the lowest Fs = 25 Hz, for now we'll assume it's the lowest tuning with the highest being ~40 Hz based on averaging everything out, though sealed is theoretically looking best overall if there's some half decent room gain.

You can use a rectangular duct vent, it's just more hassle to adjust its length and why I suggested a removable vent plate.

Anyway, looks like ~25 Hz Fb = 16.875" W x 3" H slot x 4" long vent and baffle thickness cutout = ~30 Hz, so this would be the minimum size cutout spaced up off the cab floor ~3".

GM

Ok Now I have something to work with !! Sounds Good Thanks GM !! John


:thankU: :thankU: :thankU: :lollipop::lollipop:

[GM]

You're welcome!

[Altec Best]

OK, I came up with ~18.56 ft^3 (~525.56 L) net which is about right for one driver tuned to ~30 Hz, so only ~half size for two, ergo raises F3 ~1.4x into the 40s, but corner loading hopefully will shift it back down a bit and with 107+ dB/sens/stereo +room/corner gain there's plenty for shelving EQ to flatten it out to Fb in-room.

Since the lowest Fs = 25 Hz, for now we'll assume it's the lowest tuning with the highest being ~40 Hz based on averaging everything out, though sealed is theoretically looking best overall if there's some half decent room gain.

You can use a rectangular duct vent, it's just more hassle to adjust its length and why I suggested a removable vent plate.

Anyway, looks like ~25 Hz Fb = 16.875" W x 3" H slot x 4" long vent and baffle thickness cutout = ~30 Hz, so this would be the minimum size cutout spaced up off the cab floor ~3".

GM

Are you saying vent length of Total 4" or with the baffle 3/4" + 4" Total 4.75" ? Please clarify.One other thing, I understand about the removable vent plate, but if it was going to be a utility gray i would have gone that route.But since I'm using a very nice veneer I think it looks better keeping the baffle all one piece.

Now would using round tubes be an option.I think they maybe easier to find in cardboard if tubes are used but i would need at least 4 at 3" diameter and 4" length correct ? I personally think the rectangular vent is better looking but would like to have options if I need some.

[Panomaniac]

Well I was thinking what you might do is have the vent hole cut 1.5" larger, then make several square tube vents of different lengths that you can put in there. Make the vent tubes of 3/4" material. Once you find the right length, have the small edge that shows veneered.

It's an idea, anyway.

[westend9]

If there is accomodation to get back into the cabinet, a removable bottom, back, top, or front, you could cut the front baffle port opening to the correct minimum size and use a separate port "box" of any length to attach to the back of the front baffle. Cleats are going to be your friend in that type of construction.

I've almost relegated myself to a two part front baffle for my Altec cab's. There is just no easy way around getting back into the cabinet should the need arise. I can see a change of stuffing density and port modification as two of the reasons to allow for that.

[valhallax]

sealed alignment...now thats where i'd start, before i cut any vents. so accurate, so fast. or tune to 16 hz...hmmm

[GM]

Are you saying vent length of Total 4" or with the baffle 3/4" + 4" Total 4.75" ?

But since I'm using a very nice veneer I think it looks better keeping the baffle all one piece.

Now would using round tubes be an option.

Total vent length, so for a 0.75" thick cutout, its matching duct would be 3.25" long.

OK, then Pano's suggestion is one option, though I suggest you use WE9's cleats regardless and make them beefier if rear mounted.

Cardboard tubes are fine if a grill is used, but are generally a pain to make nice looking, so plastic pipe is your friend here for typical size vents. If you work it out though, the slot is a close enough 8" i.d. pipe, but 8" o.d. is what's available and fairly expensive. OTOH, cardboard tube diameters are i.d. IIRC and it's large enough to fairly easily paint or wallpaper (been there, done that).

(8) 3" plastic pipes would work, though for 25 Hz they would need to be around 5" long each due to wall friction losses. These could be attached to a removable veneered plate with just a long slot in the baffle. WRT to blind fastening it, Velcro it with the heavy duty grade. Be careful though, use too much and you'll need a crowbar to remove them.

If you're dead set on a one piece baffle though, might as well leave it finished and use side vents.

GM

[Altec Best]

All great ideas, Thanks Guys !! :2thumbsup: I will have the ports done last to allow for collaboration. Hmmm now I really don't know what to do.What is the easiest to do here.At this point in the game i'm ready to get them done ASAP. I'm ready to get them home so the real fun can start "Tweaking" that reminds me, I think I need a Crossover real soon ! :lollipop:

Thanks Again Guys !

[GM]

Easiest? Get some ~6" diameter plastic drain pipe and either just cut snug fit holes in the bottom back left/right corner sides to corner load each vent to reduce their otherwise increased length some (all?) or make small removable grill plates for a more finished look.

Again, these will be big enough to warrant an internal mounting flange to double up the mounting thickness.

GM